This invention relates to an oven and more particularly to a cooking oven for cooking foodstuffs by means of either steam, dry convection hot air or moist convection hot air.
In particular, this invention relates to a food cooking oven which may be operated in three distinct cooking modes and wherein the oven is operated at atmospheric pressure. Cooking may be accomplished in an atmosphere of steam which has been generated within the oven cavity, by means of convection hot air to which water vapor has been added, or by means of dry convection hot air.
Prior art food preparation ovens have been provided which cook or bake food by means of convection air and wherein moisture is added to the oven cavity to prevent the food from drying out and to provide high quality prepared food. Such ovens do not have the ability to cook food by means of steam and therefore do not have the advantages of ovens wherein food is cooked by means of steam. Steam is a very effective heat transfer medium since the latent heat of vaporization needed to turn water into steam requires a great deal of thermal energy. When the steam condenses on a food product, this thermal energy will be given up directly to the food product. Steam is, therefore, a much more effective heat transfer medium than is hot air. By cooking food products in an oven in an atmosphere of steam, a great deal of energy will, therefore, be rapidly transferred to the food products. An additional benefit of cooking food products with steam is that it prevents drying out of the food products as would occur if the food product were cooked with dry, hot convection air. It is therefore desirable, in order to provide a cooking oven wherein food can be prepared quickly and efficiently, to circulate steam continuously within the oven cavity to cook the food products located therein. Furthermore, since the steam in the oven cavity will continuously condense on the food products as well as on the oven walls, it is desired to continuously generate more steam and to supply this steam continuously to the oven cavity.
It is also desired to provide a versatile oven which can cook food products in three distinct modes so that the food may be cooked either with steam only, with convection hot air to which water vapor has been added, or with dry convection hot air.
Some prior art steamer ovens have been provided wherein the condensed steam is collected in the bottom of the oven where it is reheated and reconverted to steam for recirculation in the oven. A problem with these types of ovens is that food, as it is cooked, will lose a certain amount of moisture or juice, which moisture will collect in the bottom of the oven and mix with the condensed steam. Therefore, the condensate reheating process in such prior art ovens reheats not only the condensed steam but also the collected food juices. Steam generated from this collected combined steam condensate and food juice will contain a certain amount of flavoring derived from the collected food juices. If several foods are prepared in the oven at one time, this food flavoring will be deposited on all of the food as the regenerated steam condenses and, therefore, will affect the flavor and taste of the foods, which is, of course, undesirable. It is, therefore, desired to provide an oven wherein the juices which are cooked out of the foods are disposed of so that they will not adversely affect the flavor of the foods in the oven.
Still other prior art steamer ovens have been provided wherein an external steam generator is provided to generate the steam, which is then transferred into the oven cavity. The structure of such prior art ovens is rather complicated and the ovens are, therefore, relatively expensive. Furthermore, since some of the thermal energy in the steam is lost during the transfer of the steam from the steam generator to the oven cavity, the steam used in these ovens is generally lower in temperature than desired and these prior art ovens are also relatively inefficient in the use of energy. It is, therefore, desired to provide a food preparation oven wherein steam is generated in the oven cavity by means of a simple and reliable steam generator.
Yet other types of prior art steamer food preparation apparatuses have been provided wherein the cooking cavity is pressurized. Such apparatuses tend to be relatively complex and must be provided with complicated, and therefore expensive, sealing structures, which of course is undesirable. It is, therefore, desired to provide a cooking oven for cooking foodstuffs by means of steam or convection air wherein the oven cavity is operated at atmospheric pressure.
A still further problem with prior art steamer food preparation ovens has been that the water from which the steam is generated generally contains some dissolved minerals. These minerals will remain behind when the water is turned into steam. With time, the minerals tend to collect in the steam generating apparatus and on the walls of the oven, thus leading to operational difficulties over a period of time as well as causing unsightly deposits. It is, therefore, desired to provide a steam and convection oven wherein such undesirable mineral deposits are minimized or eliminated.
Still further food preparation ovens have been provided wherein food is cooked by means of dry convection hot air. While such ovens operate satisfactorily for certain food products, in certain situations it is desired to cook food by means of hot air to which water vapor has been added or to cook food by means of steam. It is, therefore, desired to provide a versatile oven which may be operated in three modes so that the most suitable cooking mode may be selected for preparing food.